Sensing foley catheter

ABSTRACT

Foley type catheter embodiments for sensing physiologic data from a urinary tract of a patient are disclosed. The system includes the catheter and a data processing apparatus and methods for sensing physiologic data from the urinary tract. Embodiments may also include a pressure sensor having a pressure interface at a distal end of the catheter, a pressure transducer at a proximal end, and a fluid column disposed between the pressure interface and transducer. When the distal end is residing in the bladder, the pressure transducer can transduce pressure impinging on it into a chronological pressure profile, which can be processed by the data processing apparatus into one or more distinct physiologic pressure profiles, for example, peritoneal pressure, respiratory rate, and cardiac rate. At a sufficiently high data-sampling rate, these physiologic data may further include relative pulmonary tidal volume, cardiac output, relative cardiac output, and absolute cardiac stroke volume.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/583,730, filed May 1, 2017 (now U.S. Pat. No. 10,952,659 issued Mar.23, 2021), which is a continuation of U.S. patent application Ser. No.13/414,307, filed Mar. 7, 2012 (now U.S. Pat. No. 9,662,058 issued May30, 2017), which claims the benefit of U.S. Provisional Application No.61/464,619, filed Mar. 7, 2011; U.S. Provisional Application No.61/628,534, filed Nov. 2, 2011, and U.S. Provisional Application No.61/583,258, filed Jan. 5, 2012. Each of these applications isincorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The disclosed technology relates to the field of medical devices, inparticular devices capable of sensing physiologic data based on sensorsincorporated into a catheter adapted to reside in the a urinary tract ofa patient.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if each suchindividual publication or patent application were specifically andindividually indicated to be so incorporated by reference.

BACKGROUND OF THE INVENTION

The Foley catheter, named for Dr. Frederick Foley who first described aself-retaining balloon catheter in 1929, has been in use since the1930's, in a form nearly identical to its early models. In its mostbasic form, a Foley catheter has proximal portion that remains outsidethe body, a length that traverses the urethra, and a distal end thatresides in the urinary bladder. The Foley catheter is held in place byan inflatable balloon that stabilizes the device in place, and preventsinadvertent withdrawal from the bladder. A typical Foley catheterincludes at least two lumens along its length; one lumen serves as aconduit that drains the bladder, and the second lumen serves as an airconduit that allows the balloon to be controllably inflated anddeflated.

Various developments have added diagnostic functionality to Foley typecatheters, including the ability to measure pressure and temperature.For example, U.S. Pat. No. 5,389,217 of Singer discloses a catheter withoxygen sensing capability. U.S. Pat. No. 5,916,153 of Rhea and U.S. Pat.No. 6,434,418 of Neal both disclose a pressure sensor associated with aFoley type catheter. U.S. Pat. No. 6,602,243 to Noda discloses atemperature sensor associated with a Foley type catheter.

The Foley catheter, widespread in use, having a low cost, and easily putin place by health care professionals may offer still furtheropportunity as a vehicle for deriving critical diagnostic information.The technology disclosed herein provides for the delivery of highlyresolved and previously unavailable diagnostic information, as may bederived from a Foley catheter with pressure sensing capability.

SUMMARY OF THE INVENTION

The disclosed technology relates to a Foley type catheter for sensingphysiologic data from the urinary tract of a patient, the physiologicdata particularly including those gathered by high fidelity pressuresensing and transduction into signals suitable for processing. In someembodiments, the pressure-sensing Foley type catheter may further beenabled to sense temperature and analytes of clinical significance.

Embodiments of the Foley type catheter include a pressure sensor havinga pressure interface disposed at a distal end of the catheter, apressure transducer at a proximal end of the catheter, and a fluidcolumn disposed between the pressure interface and the pressuretransducer. When an embodiment of catheter is appropriately orfunctionally inserted into the urinary tract of a patient and the distalend is residing in the bladder, the pressure transducer can transducepressure impinging on it from the pressure interface into achronological pressure profile. The pressure profile has sufficientresolution to be processed into one or more distinct physiologicpressure profiles, including peritoneal pressure, respiratory rate, andcardiac rate.

In some particular embodiments of the Foley type catheter, the pressureprofile generated by the pressure sensor has sufficient resolution suchthat, when sampled by a transducer at a frequency of at least about 1Hz, it can be processed to yield a relative pulmonary tidal volumeprofile. In still further embodiments of the Foley type catheter, thepressure profile generated by the pressure sensor has sufficientresolution such that, when sampled by a transducer at a frequency of atleast about 5 Hz, it can be processed to yield physiologic pressureprofiles selected from a group consisting of cardiac output, relativecardiac output, and absolute cardiac stroke volume.

In various embodiments of the catheter, the fluid within the fluidcolumn may include a gas, such as air or carbon dioxide, or it mayinclude a liquid. In some embodiments wherein the fluid column includesa liquid, such liquid may include urine, as sourced from the bladder.

In various embodiments of the catheter, the pressure interface mayinclude an elastic membrane or a substantially inelastic membrane. Insome embodiments, the pressure interface is substantially homogeneousacross its surface area. In other embodiments, the pressure interfacecan be heterogeneous, having regions that vary in composition orthickness, or having features that provide an elasticity bias.

In particular embodiments of the catheter, the pressure interfaceincludes an expandable balloon. Such an expandable balloon may includeeither an elastic membrane or a substantially inelastic membrane.Embodiments of the balloon, particularly those having an inelasticmembrane, upon expansion, the balloon has a volume in the range of about0.1 cc to about 2 cc. Other embodiments of the balloon, upon expansion,may have larger volumes, for example, in a range of about 2 cc to about5 cc, or in a range of about 5 cc to about 250 cc, a volume that isgreater than 250 cc. In another aspect, upon inflation, embodiments ofthe balloon may have a diameter that ranges between about 6 mm and 8 mm.

In various embodiments of the catheter, the pressure interface includesa membrane arranged across an opening. In such embodiments, the membraneis sufficiently elastic to respond to an internal-external pressuredifferential across its surface.

In some embodiments, the Foley type catheter further includes atemperature sensor to monitor a body core temperature of the patient. Inthese embodiments, the physiologic data from the temperature sensor inthe system may be used to monitor body temperature and to feedbackcontrol delivery of a hypothermic treatment regimen. Temperaturessensors appropriate for the Foley type catheter may be of anyconventional type, including by way of example, a thermistor, athermocouple, or an optical temperature sensor.

In some embodiments, the Foley type catheter further includes one ormore analyte sensors. Analyte sensors included in the scope of thedisclosed technology include sensors for analytes of any clinicalsignificance. For broad examples, such analytes may include any analyteselected from a group including pH, a gas, an electrolyte, a metabolicsubstrate, a metabolite, an enzyme, or a hormone. By way of particularexamples, such analyte sensor may be able to sense any of a metabolicsubstrate or a metabolite, the analytes may include glucose or lacticacid. By way of example of a hormone, the analyte may include cortisol.

In some embodiments, the Foley type catheter further includes one ormore electrodes arranged as electrical activity sensors. Such electricalactivity sensors may deliver physiologic data that can be transformed toyield an electrocardiogram (EKG) or an electrogastrogram (EGG).

In some embodiments, the Foley type catheter further includes a lightsource and a light sensor, the sensor configured to capture lightemitted from the light source. In some embodiments, by way of example,the light source and the light sensor may be configured to operate as apulse oximeter, the light sensor being able to deliver a signal that canbe transduced into a pulse rate. In another example, the light sourceand the light sensor may be configured to operate as an analyte sensor.

Some embodiments of the Foley type catheter may further include anexpandable pressure-delivery balloon disposed on the catheter so as,upon expansion, to contact a wall of the bladder or the urethra; and alight source and a light sensor disposed proximate thetissue-compressing balloon. The pressure delivery balloon, the lightsource, and the light sensor may be arranged such that when theexpandable pressure balloon is expanded so as to blanche a tissuesurrounding it as detected by the light sensor, a light-based signalfrom the light sensor may be processed to yield a perfusion pressure ona urinary bladder wall or a urethra.

Some embodiments of the disclosed technology relate to a Foley typecatheter for sensing pressure-based physiologic data from the urinarytract of a patient having a pressure sensor that includes a pressureinterface and a transducer, the sensor not including apressure-transmitting column. These embodiments typically have apressure sensing mechanism or transducer proximate the pressureinterface. Such pressure sensors may include, by way of example, any ofa piezoelectric electric mechanism, an optical sensing mechanism, amicroelectricalmechanical (MEMS) mechanism, or an acoustic wave sensingmechanism. When the catheter is appropriately or functionally insertedinto the urinary tract and the distal end is residing in the bladder,the pressure sensor can transduce pressure impinging on it from thepressure interface into a chronological pressure profile, the pressureprofile having sufficient resolution to allow differentiation into oneor more physiologic pressure profiles selected from the group consistingof peritoneal pressure, respiratory rate, and cardiac rate.

The disclosed technology relates to a Foley type catheter for sensingpressure-based physiologic data from the urinary tract of a patient, assummarized above, but further being enabled to sense a physiologicresponse to the delivery of pressure, and thereby to determine tissueperfusion pressures. Embodiments of the Foley type catheter include apressure sensor having a pressure interface disposed at a distal end ofthe catheter, a pressure transducer at a proximal end of the catheter,and a fluid column disposed between the pressure interface and thepressure transducer. Embodiments of this type further include anexpandable pressure-delivery balloon disposed on the catheter so as,upon expansion, to contact a wall of the bladder or the urethra, and alight source and a light sensor disposed proximate thetissue-compressing balloon. When an embodiment of catheter isappropriately or functionally inserted into the urinary tract with thedistal end residing in the bladder, the pressure transducer cantransduce pressure impinging on it from the pressure interface into achronological pressure profile. The pressure profile has sufficientresolution to be processed into one or more distinct physiologicpressure profiles, including peritoneal pressure, respiratory rate, andcardiac rate. And when the expandable pressure balloon is expanded so asto blanche a tissue surrounding it (as detected by the light sensor), alight-based signal emanating from the light sensor may be processed toyield a perfusion pressure on a urinary bladder wall or a urethra.

The disclosed technology further relates to a system for sensing andprocessing physiologic data from the urinary tract of a patient, thephysiologic data particularly including those gathered by high fidelitypressure sensing and transduction into signals suitable for processing;these embodiments will now be summarized. In some embodiments, thepressure-sensing Foley type system may further be enabled to sense andprocess temperature data and/or analyte data of clinical significance;these features and embodiments will be summarized further, below.

Thus, particular embodiments of the disclosed technology relate to asystem for sensing pressure-based physiologic data from the urinarytract of a patient. Embodiments of the system include a Foley typecatheter with a pressure sensor having a pressure interface disposed ata distal end of the catheter, a pressure transducer at a proximal end ofthe catheter, and a fluid column disposed between the pressure interfaceand the pressure transducer. When the catheter is appropriately orfunctionally inserted into the urinary tract and the distal end isresiding in the bladder, the pressure transducer can transduce pressureimpinging on it from the pressure interface into a chronologicalpressure profile. Embodiments of the system further include a dataprocessing apparatus in communication with the pressure transducer so asto be able to acquire the physiological data. Embodiments of the dataprocessing apparatus are configured to process the chronologicalpressure profile into one or more physiologic pressure profiles from thegroup including peritoneal pressure, respiratory rate, and cardiac rate.

In particular embodiments of the system, the pressure transducer isoperable to sample pressure impinging on it at a rate of at least about1 Hz. In embodiments such as these, the data processing apparatus may beconfigured to determine relative pulmonary tidal volume. In otherparticular embodiments of the system, the pressure transducer isoperable to sample pressure impinging on it at a rate of at least about5 Hz. In embodiments such as these, the data processing apparatus may beconfigured to determine any of cardiac output, relative cardiac output,or absolute cardiac stroke volume.

In particular embodiments of the system, the Foley type catheter mayfurther include a temperature sensor to monitor body temperature. Inembodiments such as these, the data processing apparatus may be furtherconfigured to acquire and process signals from temperature sensor.

In other embodiments of the system, the Foley type catheter may furtherinclude one or more analyte sensors. In embodiments such as these, thedata processing apparatus is further configured to acquire and processsignals from the one or more analyte sensors.

In some embodiments of the system, the data processing apparatusincludes a stand-alone console. In some embodiments, the stand-aloneconsole includes a bedside unit that is dedicated to monitoring a singlepatient. In some of these types of embodiments, the communicationbetween the pressure transducer and the data processing apparatus iswireless.

In some embodiments of the system, the data processing apparatusincludes a networked computer. In some of these types of embodiments,the networked computer is able to track data from a plurality ofpatients.

In particular embodiments of the system, the data processing apparatusmay include both a stand-alone console and a networked computer. In someof these types of embodiments of this type, the stand-alone console andthe networked computer are in communication with each other. Inparticular embodiments, the in communication between the stand-aloneconsole and the networked computer is wireless.

In some embodiments of the system, the data processing apparatus mayinclude a memory into which a normal range of values for the physiologicdata may be entered, and the data processing apparatus may be configuredto initiate an alarm when physiologic data of the patient are outsidesuch range of normal values.

In some embodiments of the system, the data processing apparatus mayinclude a memory configured to receive patient-specific clinical datafrom a source external to the Foley type catheter, and the dataprocessing apparatus may be configured to integrate such external dataand the Foley type catheter-derived physiologic data.

Some embodiments of the system may include a controller in communicationwith the data processing apparatus. In such embodiments, the controllermay be configured to tune a level of pressure being applied through thefluid column against the proximal side of the pressure interface.Aspects of tuning the pressure level being applied distally against thepressure interface are expanded on below, in the context of summarizingmethods provided by the disclosure. Further, in embodiments of thecatheter that include a pressure delivery balloon that may be used in amethod to measure tissue perfusion pressure, the controller may beconfigured to controllably expand such pressure delivery balloon.

In some embodiments of the system, the physiologic data from thepressure sensor may be used to track clinical parameters relevant tomonitoring intraabdominal hypertension (IAH) or abdominal compartmentsyndrome (ACS). In other embodiments of the system, the physiologic datafrom the pressure sensor may be used to track clinical parametersrelevant to monitoring any of cardiac status, respiratory status, theonset and progression of hemorrhage or shock, patient bodily movement,or intestinal peristalsis.

As noted above, some embodiments of the disclosed technology relate to asystem for sensing pressure-based and temperature-based physiologic datafrom the urinary tract of a patient, such system including a Foley typecatheter with a pressure sensor and a temperature sensor. Embodiments ofthe pressure sensor have a pressure interface disposed at a distal endof the catheter, a pressure transducer at a proximal end of thecatheter, and a fluid column disposed between the pressure interface andthe pressure transducer. When the catheter is appropriately orfunctionally inserted into the urinary tract and the distal end isresiding in the bladder, the pressure transducer transduces pressureimpinging on it from the fluid column into physiological data comprisinga chronological pressure profile. Embodiments of the system furtherinclude a data processing apparatus in communication with the pressuretransducer so as to be able to acquire the physiological data.Embodiments of the data processing apparatus are configured to processthe chronological pressure profile into one or more physiologic pressureprofiles from the group including peritoneal pressure, respiratory rate,and cardiac rate. Embodiments of the data processing apparatus arefurther configured to acquire and process signals from the temperaturesensor, such signals reporting the core body temperature of the patient.

Some embodiments of the disclosed technology relate to a system forsensing pressure-based and analyte-based physiologic data from theurinary tract of a patient, such system including a Foley type catheterwith a pressure sensor and one or more analyte sensors. Embodiments ofthe pressure sensor have a pressure interface disposed at a distal endof the catheter, a pressure transducer at a proximal end of thecatheter, and a fluid column disposed between the pressure interface andthe pressure transducer. When the catheter is appropriately orfunctionally inserted into the urinary tract and the distal end isresiding in the bladder, the pressure transducer transduces pressureimpinging on it from the fluid column into physiological data comprisinga chronological pressure profile. Embodiments of the system furtherinclude a data processing apparatus in communication with the pressuretransducer so as to be able to acquire the physiological data.Embodiments of the data processing apparatus are configured to processthe chronological pressure profile into one or more physiologic pressureprofiles from the group including peritoneal pressure, respiratory rate,and cardiac rate. Embodiments of the data processing apparatus arefurther configured to acquire and process analyte signals from the oneor more analyte sensors, such signals reporting the level of one or moreanalytes within the urinary tract.

As noted above, some embodiments of the disclosed technology relate to asystem for sensing pressure-based, temperature-based, and analyte-basedphysiologic data from the urinary tract of a patient, such systemincluding a Foley type catheter with a pressure sensor, a temperaturesensor, and one or more analyte sensors. Embodiments of the pressuresensor have a pressure interface disposed at a distal end of thecatheter, a pressure transducer at a proximal end of the catheter, and afluid column disposed between the pressure interface and the pressuretransducer. When the catheter is appropriately or functionally insertedinto the urinary tract and the distal end is residing in the bladder,the pressure transducer transduces pressure impinging on it from thefluid column into physiological data comprising a chronological pressureprofile. Embodiments of the system further include a data processingapparatus in communication with the pressure transducer so as to be ableto acquire the physiological data. Embodiments of the data processingapparatus are configured to process the chronological pressure profileinto one or more physiologic pressure profiles from the group includingperitoneal pressure, respiratory rate, and cardiac rate. Embodiments ofthe data processing apparatus are further configured to acquire andprocess signals from the temperature sensor, such signals reporting thecore body temperature of the patient. Embodiments of the data processingapparatus are further configured to acquire and process analyte signalsfrom the one or more analyte sensors, such signals reporting the levelof one or more analytes within the urinary tract.

In some embodiments of the system, the physiologic data from the any oneor more of the sensors (pressure sensor, temperature sensor, and/oranalyte sensor) may be used to track clinical parameters particularlyrelevant to monitoring clinical conditions brought about by metabolicdiseases or diseases with pathophysiologic metabolic symptoms. Forexample, embodiments of the system may be used to monitor clinicalparameters relevant to kidney function or diabetes. In other embodimentsof the method, the physiologic data from the sensors, the pressuresensor in particular, may be used to monitor body movement.

Some embodiments of the system include a fluid-collecting receptacle tocollect urine drained from the bladder, and the receptacle may include afluid volume measuring system. In some of such embodiments, the fluidvolume measuring system is configured to deliver data from which a urineoutput rate may be determined. Embodiments of the fluid volume measuringsystems may include any of a weight-sensitive system, a fluid heightsensing system, a mechanical mechanism, or an optically-sensitivesystem.

Some embodiments of the fluid-collecting receptacle may include achemical analyte measuring system to identify and/or quantitate analytessuch as those summarized for the Foley type catheter itself. Morespecifically, as example, analyte sensors may be sensitive to any one ormore analytes selected from a group consisting of bacteria, blood,hemoglobin, leukocyte esterase, glucose, and particulate matter.

Some embodiments of the fluid-collecting receptacle may include an RFIDchip for identification of the receptacle in communications with a dataprocessing apparatus, or for conveying sensed data to the dataprocessing apparatus.

Some embodiments of the system may include a docking station toaccommodate the collecting receptacle, wherein the docking station andthe collecting receptacle are in electrical communication with eachother. Communication between the docking station and the collectingreceptacle may occur by way of a data transmission line connecting thedocking station to the console, or it may occur by way of a wirelesscommunication system.

Some embodiments of the system may include a fluid infusion apparatus,with the data processing apparatus being configured to control theactivity of the fluid infusion apparatus in response to physiologic dataprocessed by the data processing apparatus.

Some embodiments of the disclosed technology relate to a method formonitoring physiologic data from the urinary tract of a patient. Thesephysiologic data particularly include pressure-based data, but mayfurther include temperature-based data and analyte-based data. In stillfurther embodiments, delivery of pressure in combination withlight-based data to yield tissue perfusion pressure values.

Embodiments of the method include providing a physiologic datamonitoring system that includes a Foley type catheter and a dataprocessing apparatus. Embodiments of the Foley type catheter have apressure sensor, the pressure sensor having a pressure interfacedisposed at a distal end of the catheter, a pressure transducer at aproximal end of the catheter, and a fluid column disposed between thepressure interface and the pressure transducer, the pressure transducerbeing able to transduce pressure impinging on it from the fluid columninto physiological data comprising a chronological pressure profile. Themethod may further include inserting the Foley type catheter in theurinary tract such that the pressure interface is residing within thepatient's bladder; transferring pressure sensed in the bladder into atransducible chronological pressure profile; and processing thechronological pressure profile into one or more physiologic pressureprofiles selected from the group consisting of peritoneal pressure,respiratory rate, and cardiac rate.

Some embodiments of the method include tuning or priming a level ofpressure being applied from a proximal side of the pressure interface ofa Foley type catheter toward equivalence with a baseline physiologicpressure being applied to a distal side of the pressure interface.Tuning pressure refers generally to either increasing or decreasingpressure applied to the proximal side of the pressure interface.Proximal, in this context, refers to the side of the pressure interfacefacing outward from the body (within the communicating fluid column),and toward the main body of the catheter or an operator handling thecatheter. In one aspect, tuning the pressure level may refer to primingthe fluid column from the proximal end of the column, directing pressuretoward the distal end of the column. In another aspect, tuning thepressure level may refer to releasing or bleeding pressure from theproximal end of the column, as may be appropriate, for example, ifpressure in the column overshoots a desired pressure level, or ifpressure from within the bladder were to decrease. Embodiments of themethod may further include repeating the tuning step, as needed, tomaintain equivalence between the level of pressure being applied fromthe proximal side of the pressure interface and the baseline physiologicpressure being applied to a distal side of the pressure interface.

Embodiments of the tuning step of the method may include monitoring aphysiologic pressure profile, and adjusting the pressure being appliedfrom a proximal side of the pressure interface to a level such that aquality of a physiologic pressure profile being processed by the systemis optimized. By way of example, the amplitude of pressure wavesassociated with the respiratory rate may be monitored. A high amplitudepressure profile may be considered optimal in that it is generallyassociated with conditions of equivalence between baseline pressure oneither side of the pressure interface. In another aspect, a highamplitude pressure profile may be considered optimal because, otherfactors being equal, a high amplitude signal permits a higher level ofresolution of real differences that may appear in signal level. In someembodiments, the monitoring step may be performed automatically by thedata processor, and the adjusting step may be performed by an automaticcontroller in communication with the data processor.

The necessity to prime the catheter is driven, at least in part, byleakage of gas from the fluid column. It has been observed, for example,that a Foley type catheter, per embodiments of the disclosed technology,that comprises a thin silicone membrane (e.g., a membrane with athickness of 0.003 inch) leak about 2 cc of air per hour when under 15mm Hg of pressure.

Some embodiments of the method may include applying pressure to theproximal side of the pressure interface by delivering gas under pressureto a space proximal to the pressure interface. Delivering gas to thespace proximal the pressure interface may be considered priming thespace or tuning the space so as to equilibrate or substantiallyequilibrate pressure on either side of the pressure interface. Thesource of the gas, per embodiments of the technology, is typically acompressed gas cylinder. Any suitable biologically compatible gas may beused, including, by way of example, air or carbon dioxide.

In some embodiments of the method, appropriate for those in which thepressure interface includes a balloon formed from an inelastic membrane,the method further includes priming the fluid column from the proximalend of the catheter to maintain the balloon at a size that places nosubstantial strain on the inelastic membrane.

In some embodiments of the method, appropriate for those in which thepressure interface includes a balloon formed from an inelastic membranehaving a total surface area, the method further include inflating theballoon to a level such that the total surface area of the membrane issubstantially taut.

Some embodiments of the method include sampling the pressure profileimpinging on the transducer at a frequency of at least 1 Hz, the methodfurther comprising quantifying respiratory excursions relative to abaseline magnitude of excursions proximate the time of catheterinsertion. These embodiments may particularly include monitoring therelative amplitude of respiratory pressure wave excursions, and relatingsuch relative amplitude to relative respiratory tidal volumes.

Some embodiments of the method include sampling the pressure profileimpinging on the transducer at a frequency of at least 5 Hz, the methodfurther including quantifying peaks on the respiratory pressure wavethat are associated with the cardiac rate. In particular embodiments ofthis type, against a background of a substantially stable peritonealpressure, the method may further include determining any of cardiacoutput, relative cardiac output, respiratory tidal volume, or absolutecardiac stroke volume.

In some embodiments of the method, the one or more physiologic pressureprofiles yielded by processing the chronological pressure profile mayprovide for monitoring of body movement. Monitoring body movement may beof particular benefit for bed-ridden patients, for example, who have adecubitis ulcer, or are at risk of developing such an ulcer when aportion of the body, such as a bony prominence, rests too long in apressured position without movement that would relieve such pressure.Accordingly, monitoring body movement may include notifying a healthcare provider of the level of movement of a patient who is at risk ofdeveloping a decubitis ulcer, or at risk of exacerbating an existingdecubitis ulcer. In addition, monitoring of patient activity may alsoaffirmatively report the presence of movement. In this case, a patientthat is a fall risk can be monitored for activity that may indicate anattempt to rise from their bed. This may signal an alert and preventtheir mobility without assistance.

In some embodiments of the method, wherein the Foley type catheter hasan expandable pressure delivery balloon, a light source and a lightsensor proximate the expandable pressure balloon (the light sensorconfigured to capture light from the light source) the method mayfurther include inflating the pressure delivery balloon to a desiredpressure, and monitoring the pressure within the expandable balloon todetermine the pressure level required to blanche the tissue, saidblanching pressure being reflective of a tissue perfusion pressure.

In some embodiments of the method, wherein the Foley type catheter has atemperature sensor, the method may further include monitoring the bodytemperature of the patient. In some embodiments of the method, whereinthe Foley type catheter further comprises an analyte sensor, the methodfurther may further include monitoring a level of the analyte within theurine of the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a data console in communication with a urine-collectingreceptacle docking station, per an embodiment of the sensing Foleycatheter system.

FIG. 2 shows an embodiment of the sensing Foley catheter system set upto measure urine output from a human subject.

FIG. 3 shows an embodiment of the sensing Foley catheter system set upas an automated infusion therapy system for a human subject.

FIG. 4 shows a volume-sensing urine collecting receptacle that includesan RFID chip, the receptacle accommodated within a receptacle dockingstation, per an embodiment of the sensing Foley catheter system.

FIG. 5A shows a sensing Foley catheter with a pressure interface in theform of an inflatable balloon, per an embodiment of the sensing Foleycatheter system.

FIG. 5B shows a sensing Foley catheter a pressure interface in the formof a membrane arranged across a luminal opening, per an embodiment ofthe sensing Foley catheter system.

FIGS. 6A-6D show various views and details of a sensing Foley catheter,per an embodiment of the sensing Foley catheter system. FIG. 6Aschematically arranges the sensing Foley catheter into a proximalsection that remains external to the body when in use, a portion thatresides in the urethra, and a portion that resides in the bladder, whenplaced into a human subject.

FIG. 6B shows a detailed view of the proximal portion of the catheter.

FIG. 6C shows a cross sectional view of the central length of thecatheter.

FIG. 6D shows a detailed view of the distal portion of the catheter thatresides in the bladder.

FIG. 7A shows an example of respiratory rate sensing data from a humansubject, as provided by an embodiment of the sensing Foley cathetersystem. During this test period, the subject performs a respiratorysequence as follows: (1) breath being held at the end of an expiration,(2) valsalva, (3) normal respiration, (4) valsalva, and (5) breath beingheld at the end of an expiration.

FIG. 7B shows a detailed portion of the respiratory profile of FIG. 7A,a portion of the period of normal respiration.

FIG. 8 shows an example of cardiac rate and relative cardiac outputsensing data from a human subject, as provided by an embodiment of thesensing Foley catheter system, and an EKG trace as measuredsimultaneously and independently.

FIG. 9 shows data related to relative cardiac output sensing in a humanleg raising exercise in which cardiac output increases, as demonstratedby an increased amplitude of the cardiac pulse.

FIG. 10 shows an example of peritoneal sensing data, with a focus onrespiratory rate from a pig, as provided by an embodiment of the sensingFoley catheter system.

FIG. 11 shows an example of pig study that demonstrates the capabilityof an embodiment of the sensing Foley catheter system to detectintra-abdominal hypertension.

FIG. 12 shows intraabdominal pressure, respiratory wave pressure, andcardiac pressure schematically arrayed as a two dimensional plot ofpressure (mm Hg on a logarithmic scale vs. frequency (Hz).

FIG. 13 provides a flow diagram of an embodiment of the method.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIGS. 1-4 show various elements of the disclosed technology, including aurine receptacle 60 (holding a urine output 61), a docking station 65 tohold the receptacle, an electrical connection 67 that allowscommunication between the docking station and a data collection andprocessing apparatus in the form a bedside console 80. Embodiments ofthe urine collecting receptacle 60 may include level or volume sensors62, as well as other analyte sensors. Receptacle 60 may also include anRFID element that provides a unique identifier to a remote RFID reader68. In some embodiments, an extender tube 63 may be utilized to conveyurine from the catheter to the urine-collecting receptacle.

FIG. 1 shows a data receiving and processing apparatus in the form of abedside console 80 in communication with a receptacle docking station 65that accommodates a urine collecting receptacle 60, shown as holding aurine output 61, per an embodiment of the sensing Foley catheter system.The communication path between the docking station and the console mayinclude a wired connection 67, as shown, or it may be a wirelessconnection. The bedside console may record and display output/inputdata. Physiologic data from sensors associated with a sensing Foleycatheter may be held in a memory, displayed, printed, or directlytransmitted to a centralized data collection server.

In some embodiments, the bedside console or controller is portable andable to travel with the patient. Embodiments of console may beattachable to a patient's bed or an IV pole, or a wall mount; ittypically has its own display, and is able to provide critical alerts.Some embodiments of console may be adapted to be able to operate on abattery backup for 4 or more hours, as for example when wall power isunavailable or has been lost. This portability feature of console isadvantageous in situations where patients are typically not beingelectronically monitored, such as when a patient is in transit from hisor her bed to another location. Embodiments of console may also beconfigured to communicate to a base station with alerts and centralizedreporting and data collection. A controller or base station may alsogenerate mobile alerts that may be sent to nurses or healthcareprovider. Signal analysis and/or predictive algorithms may also be usedto provide useful clinical data from sensors.

FIG. 2 shows elements of an embodiment of the sensing Foley cathetersystem configured to measure urine output from a human subject. In someembodiments, the bedside console 80 or an RFID reader (see FIG. 5 ) isenabled to trigger an alert if urine output is above or below a presetnormal or desired range for urine output over a set period of time. Someembodiments of the system may also have an intravenous infusioncapability (see FIG. 3 ) to provide use sensed data to regulate deliveryof fluids or medicinal agents such as a diuretic drug, by way of anautomated system based on the urine output feedback. Embodiments of thesystem may include a docking station for the urine collectingreceptacle, the docking station being configured for data transmissionto a data receiving and processing apparatus such as a bedside consoleor a networked central computer. In some embodiments, the dockingstation delivers data regarding the volume of urine in the urinereceptacle, as well as data that are informative regarding electricalparameters of the urine, such as conductivity, resistance, or impedance.Sensors may also detect and monitor bacteria, hemoglobin, or othersubstances of clinical significance in urine.

FIG. 3 shows an embodiment of the sensing Foley catheter systemconfigured as an automated infusion therapy system for a human subject.A bedside console 80 may integrate patient data, such as fluids receivedor urine output recorded, and then automate therapeutic infusion inresponse to these data. For example, delivery of fluids or drugsolutions such as a physiological saline solution may be initiated orregulated through an infusion line 82 if the patient is dehydrated, or adiuretic may be infused if the patient is fluid overloaded. In someembodiments, the console may trigger a local alert (e.g., audiblebeeping), or trigger a centralized alert (e.g., a system alarm) if urineoutput drops too low. The console may also integrate a hydrating ormedicinal fluid infusion capability, such as an IV infusion pump, andmay adjust infusion rates based on these data or based on data acquiredfrom other sensors automatically. The console may communicatewirelessly, as well, to these and other sensors within the body.

FIG. 4 shows a volume-sensing urine receptacle 60 accommodated within areceptacle docking station 65, per an embodiment of the sensing Foleycatheter system. Embodiments of the receptacle may detect urine outputbased on the levels at which sensors 62 are triggered. For example, thereceptacle may include electrical contacts arranged as liquidheight-marks, and when an electrical path is made between two contactsand all contacts below, the level can be reported at that level.Embodiments of the receptacle may include electrical, optical, chemicalor mechanical sensors. Embodiments of the receptacle may include alsocontain diffuse or discrete sensing areas that detect analytes ofinterest, e.g., hemoglobin, protein, glucose, bacteria, blood, leukocyteesterase. Sensing or data reporting of sensed data may be of either anintermittent or a continuous nature.

Embodiments of the receptacle may include a capability to report sensingdata to the bedside console, locally (e.g., by beeping) or centrally viapiping data to a central information collection area. For example, analert may be triggered if urine output drops below 30 cc/hr. inpost-operative setting or below any otherwise predetermined threshold.Embodiments of the receptacle may connect to a docking station throughelectrical contacts; data communication among embodiments of thereceptacle, docking station, and a console or central computer may alsobe wireless. If a docking station is used, it may detect urine outputbased on weight or pressure of the receptacle that is applied to base.

Embodiments of the urine collecting receptacle may include disposable ordurable optical, electrical or chemical sensors capable of sensing andmeasuring urine content of analytes such as glucose, electrolytes,bacteria, hemoglobin, or blood. Embodiments of the receptacle mayinclude an interface with specifically designed area of the urinereceptacle to allow for this measurement, such as an optically clearwindow for optical measurement of blood. Embodiments of the receptacledocking station may also grasp or accommodate the urine receptacle inany manner so long as it secures the receptacle. The docking station orthe receptacle may include an inductive antenna or RFID capabilities toallow for wireless querying and reporting of the level of urine or otherfluid collection.

The embodiment of FIG. 4 also shows a volume-sensing urine receptacle 60that includes an RFID chip, per an embodiment of the sensing Foleycatheter system. This embodiment may contain RFID circuitry to collectand transmit data directly from within the receptacle to a remote RFIDreader 68. When queried by the RFID reader, the receptacle may detectimpedance, resistance, capacitance or any other electrical ornon-electrical property to measure the urine level and report this backto the reader. The reader may then trigger alert if urine output is outof a normal or desirable range. The RFID chip may be capable ofdetecting changes in optical, chemical, electrical, acoustic ormechanical properties, as well. RFID chips may be active or passive, andmay contain an antenna to transmit a receptacle-identifying signal tothe reader, and allow multiple receptacles to be queried simultaneously.An active RFID chip may incorporate a small battery (to extend itsrange). A passive RFID chip may be powered by the transmission from theRFID reader. The RFID reader may query a device from a distance towirelessly check the urine output level or it may be centralized toquery all receptacles within a unit, floor or hospital and issue analert if urine output is out of a normal or desirable range. The RFIDreader record urine output, as well, and functionally replace theindividual unit console shown in FIGS. 1-3 . The RFID reader may alsoreport data from other sensors within the system, including bladdertemperature or presence of analytes (as detailed elsewhere) in theurine.

FIGS. 5A-6D show embodiments of a sensing Foley catheter 10 and variousof its features. A catheter may be understood to have various sectionsaccording to their disposition when the catheter is inserted into ahuman subject, such as a proximal portion 14 that remains external tothe subject, a central or urethra-residing portion 13, and a distal orurinary bladder-residing portion 12.

Various internal lumens traverse the length of the catheter, such as anair or fluid 24 that communicates with a bladder retention balloon 36. Aurine drainage lumen 23 has a distal opening 41 that resides in thebladder portion 12 of the catheter, and has an opening at the proximalend 14 of the catheter. As seen in FIGS. 2 and 3 , the urine drainagelumen may be connected to an extender tube 63 that conveys the urine toa collecting receptacle. In some embodiments, the drainage lumen anddistal opening in the bladder may also serve as in infusion conduit (seeFIG. 3 ) by which medicinal agents may be infused, or through whichheating or cooling fluid may be infused. Analyte sensors or temperaturesensors 50 may be disposed on the catheter, either on the urethralportion 10 or the bladder-residing portion 12 of the catheter.Electrical or optical fiber leads may be disposed in a lumen 25 thatallows communication of sensing signals between distally disposedsensors and the proximal portion of the catheter, and then furthercommunication to a data processing apparatus.

An inflatable pressure-sensing balloon 38 (FIGS. 6A, 7A, and 7B) or apressure sensing membrane 39 (FIG. 5B) arranged across an opening may bepositioned on the distal end 12 of the catheter, residing in thebladder. Embodiments of a pressure-sensing balloon or pressure sensingmembrane may be understood as comprising a pressure interface having adistal-facing surface exposed to pressure from within the bladder, and aproximal-facing surface exposed to a proximal fluid column. Embodimentsof the fluid column (filled with either liquid or gas) may comprise adedicated lumen, or such column may share a lumen that also serves as asensing conduit such as lumen 25.

FIG. 5A shows a sensing Foley catheter that includes a pressureinterface in the form of pressure-sensing balloon, per an embodiment ofthe presently disclosed system. Pressure-based physiologic parametersthat this catheter embodiment can sense may include, by way of example,peritoneal pressure, respiratory rate, and cardiac rate, relativepulmonary tidal volume profile, cardiac output, relative cardiac output,and absolute cardiac stroke volume. Some embodiments of the Foley typecatheter may be further equipped with any of a temperature sensor, oneor more analyte sensors, electrodes, and paired light sources andsensors. Embodiments thus further equipped are capable of deliveringother forms of physiologic data, as for example, blood pressure, oxygensaturation, pulse oximetry, EKG, and capillary fill pressure. A pressuretransducer 20 is further shown connected at the proximal end of thecatheter external to the body.

FIG. 5B shows a sensing Foley catheter with a lumen (the third lumen,for example) used as a pressure sensing lumen; this embodiment does notinclude a dedicated pressure-sensing balloon as does the embodiment ofFIG. 5A, but instead has a pressure interface in the form of a membranearranged over a distal opening of the pressure sensing lumen. In thisembodiment, the sensing Foley catheter is able to detect and reportpressure-based physiologic data as included in the embodiment describedabove. In this present embodiment, a slow infusion of fluid into thebladder may be accomplished through the third lumen of a standard 3-wayFoley catheter, and pressure may be sensed using a pressure sensor inline with this third lumen. In this embodiment, all methods associatedwith processing and responding to pressure-based physiologic data, asdescribed for embodiments with a pressure-sensing balloon, are enabled.

FIGS. 6A-6D show various views and details of a sensing Foley catheter,per an embodiment of the sensing Foley catheter system. FIG. 6Aschematically arranges the sensing Foley catheter into a proximalsection 14 that remains external to the body when in use, a portion 13that resides in the urethra, and a distal portion 12 that resides in thebladder, when placed into a human subject. FIG. 6B shows a detailed viewof the proximal portion of the catheter, focusing on luminal openings23, 24, and 25, which are configured to make more proximal connections.FIG. 6C shows a cross sectional view of the central length of thecatheter, and an example of how lumens 23, 24, and 25 may be arranged.FIG. 6D shows a detailed view of the distal portion of the catheter thatresides in the bladder, with a particular focus on a retention balloon36 and a pressure-sensing balloon 38.

Pulse oximetry elements allow for a determination of blood oxygenconcentration or saturation, and may be disposed anywhere along theurethral length of the catheter. In some embodiments, the sensor orsensors are disposed within the tubing of the device to ensureapproximation to the urethral mucosa. With this technology, a healthcareprovider can decompress the bladder with a urinary catheter and obtainpulse oximetry data in a repeatable and accurate manner. The powersource for pulse oximetry may be incorporated within the urinarycollecting receptacle or within the catheter itself. In someembodiments, the pulse oximeter is reusable and the catheter interfaceis disposable; in this arrangement the pulse oximeter is reversiblyattached to the disposable catheter and removed when oxygen measurementsare no longer desired. Embodiments of the sensing Foley catheter mayinclude an optically transparent, or sufficiently transparent, channelfor the oximetry signal, such as a fiber-optic cable, transparentwindow, and an interface for the reusable oximeter. This method anddevice for urethral pulse oximetry may be used in conjunction with anyof the other embodiments detailed herein or may be a stand-alone device.

Embodiments of the sensing Foley catheter may be able to sense any oneor more of a plurality of clinically relevant parameters, such asincluded in the following examples: urine pH, urine oxygen content,urine nitrate content, respiratory rate, heart rate, perfusion pressureof the bladder wall or the urethral wall, temperature inside the bladderor the urethra, electro-cardiography via sensors on the bladder wall orthe urethra, respiratory volume, respiratory pressure, peritonealpressure, urine glucose, blood glucose via urethral mucosa and/orbladder mucosa, urine proteins, urine hemoglobin, blood pressure. Insome embodiments, the catheter can sense multiple parameters, but someembodiments may be limited to as few as a single parameter for focusedapplications (for example, respiratory rate in a patient in respiratorydistress). The respiratory rate, relative tidal volume, peritonealpressure, heart rate and/or relative cardiac output may be measuredsimultaneously, as well, by connecting a balloon with a flaccid wall orsemi-tense wall to an external pressure sensor via a lumen that may befilled with liquid and/or gas.

These parameters may be measured, alone or in concert with otherparameters, through the use of pressure measurement modalities otherthan the external pressure sensor. These may include: a deflectingmembrane inside of the catheter, MEMs technology, a catheter-basedsensor and/or other embodiments.

Relative cardiac output and relative tidal volume may also becalculated, based on the deflection of the pressure sensor and/or otherforce gauge. If sampled with sufficient frequency (e.g., 1 Hz orgreater), respiratory excursions can be quantified in a relative mannerto the amplitude of the excursions at the time of catheter placement.Larger excursions generally relate to heavier breathing, or in thesetting of an upward drift in the baseline, a higher peritonealpressure. The small peaks on the oscillating respiratory wave, caused bythe pumping heart, may be tracked as well by using faster sampling rates(e.g., 5 Hz or greater), and the amplitude of this wave may be used, inthe setting of a relatively constant peritoneal pressure, to determinethe relative cardiac output, in the setting of a known, stableperitoneal pressure, absolute stroke volume and/or cardiac output.

The disclosed technology captures a high-resolution chronologicalprofile (pressure as a function of time) of peritoneal pressure that canbe transduced and processed into distinct pressure profiles assignableto particular physiologic sources, including peritoneal pressure,respiratory rate, and cardiac rate. By tracking the pressure profile ata sufficiently rapid sampling rate, as provided by the technology, thepressure profile can be further resolved into relative pulmonary tidalvolume, cardiac output, relative cardiac output, and absolute cardiacstroke volume.

Accordingly, aspects of the disclosed technology relate to fidelity andresolution of a pressure signal generated in response to changes inpressure within the bladder, such changes being reflective of a pressureprofile within the peritoneal cavity, such pressure profile includingcumulative input from the aforementioned physiologic sources. Aspects ofthe technology further relate to fidelity and resolution of thetransduction of the pressure signal into a highly resolvable electricalsignal. Aspects of the technology relate still further to processing thetotality of the electrical signal profile, a surrogate for the pressureprofile within the peritoneal cavity, into component profiles that canbe assigned to the physiologic sources.

The sensitivity of an inflated balloon as a pressure sensor is afunction, in part, of the pressure differential across the balloonmembrane as a baseline condition. The balloon has the greatestsensitivity to pressure when the baseline pressure differential is nearzero. As the baseline pressure differential increases, the sensitivityof the pressure-sensing balloon degrades. Accordingly, the disclosedtechnology provides an automatic priming method that maintains theballoon in an inflated state, but with a minimal pressure differential.

Embodiments of the technology include a pressure interface as may berepresented by a balloon having either a compliant membrane or anon-compliant membrane. In general, considerations related to optimizingthe pressure around the pressure interface of the device are informed byBoyle's ideal gas law, the relationship between stress and strain asdescribed by Hooke, and by application of Young's modulus. Theconditions for optimal sensitivity of a compliant balloon and anon-compliant balloon are slightly different, although, in general, thesensitivity of each is best served by P1 and P2 being approximatelyequal. A non-compliant balloon maximum sensitivity is achieved when P1is only slightly above P2. For a compliant balloon, the maximumsensitivity is achieved when P1 is slightly above P2 at the low end ofthe (linear) elastic region of the spring constant of the compliantballoon material.

To effectively capture physiologic pressure profiles, the profiles needto be sampled at a rate that is sufficient to resolve the inherentfrequency of changes in the profile. This consideration is informed bythe Nyquist-Shannon sampling theorem, which states that a samplingfrequency of at least 2B samples/second is required to resolve an eventthat runs at a frequency of B cycles/second. As applied to a physiologicpressure cycle, for example, a cardiac rate of 70 beats/minute requiresa sampling rate of at least 140 samples/minute to effectively capturethe cycle. This relationship underlies aspects of the disclosedtechnology that specify the sampling rate particularly required tocapture physiologic pressure cycles such as relative pulmonary tidalvolume, cardiac output, relative cardiac output, and absolute cardiacstroke volume.

FIG. 12 shows intraabdominal pressure, respiratory wave pressure, andcardiac pressure schematically arrayed as a two dimensional plot ofpressure (mm Hg on a logarithmic scale vs. frequency (Hz). It can beseen that there is an inverse relationship between pressure andfrequency, and the various physiologic pressure-related parametersoccupy distinct sectors when arrayed in this manner. It is by thedistinctness of these profiles that embodiments of the method, asdisclosed herein, can resolve a single overall chronological pressureprofile into the distinct subprofiles, in accordance with theirphysiologic origin.

Expandable pressure sensing balloons, per embodiments of the technology,may assume one of at least two basic forms, type 1 or type 2. In balloonembodiments of type 1, which may be generally likened to a conventionalparty balloon, the pressure-sensing balloon is formed from or includes acompliant or elastic membrane. Accordingly, the surface area of themembrane expands or contracts as a function of the expansion of theballoon. The elasticity of the membrane determines various features ofthe balloon, as a whole, at different levels of expansion. Uponexpansion, the balloon, if unconstrained, maintains a substantiallyconstant or preferred form or shape, as determined by the mandrel uponwhich the balloon is formed. Upon expansion of the balloon from aminimal volume to its maximal volume, the membrane of the balloonmaintains a level of tautness. Within the limits of elasticity of thecompliant membrane, an increase in pressure during inflation results ina consequent expansion of volume. The balloon, on the whole may beconsidered partially compliant in that its shape responds to spatialconstraints that it may encounter upon expansion or inflation, howeverthe balloon does have a preferred or native shape, and such shapepreference prevents a level of shape compliance or conformability suchas that shown by a balloon of type 2.

In balloon embodiments of type 2, the expandable pressure-sensingballoon is formed from or includes a non-compliant, or non-elasticmembrane, or a membrane that is substantially non-compliant ornon-elastic. Accordingly, the surface area of the membrane does notexpand or contract in accordance with the level of balloon expansion.Type 2 pressure-sensing balloons may be generally likened to aconventional Mylar® balloon. The inelasticity of the membrane determinesvarious features of the balloon, as a whole, at different levels ofexpansion. Upon expansion of the balloon from a minimal volume to alevel near its maximal volume, the membrane of the balloon is supple,and has a level of slackness. Expansion of a type 2 balloon occurs byway of outwardly directed smoothing of wrinkles and folds in themembrane. Deflation or compression of a type 2 balloon occurs by way ofgenerally inwardly directed wrinkling and infolding. When a type 2balloon is fully inflated (or substantially inflated) without being in aconfining space, it assumes a preferred or native shape as determined bythe geometry of the membrane or fabric of the balloon. However, in astate of partial inflation, the balloon, as a whole, is highly suppleand conformable, broadly taking the shape as may be dictated by aconfining space.

Expandable pressure sensing balloons, per embodiments of the technology,may also include features of both of the two basic forms, type 1 or type2. In these embodiments, the membrane may include regions that areelastic (like type 1) and regions that are inelastic (like type 2). Aballoon of this hybrid type would, as a whole, behave in a mannerdrawing from behavioral aspects of both type 1 and type 2 balloons, asdescribed above. Further, type 1 balloons may be formed with a membranethat is not of a homogeneous composition or thickness. In suchembodiments, regions of different thickness or composition could havevarying degrees of elasticity, thus affecting the behavior of theseregions during expansion of the balloon. In still other embodiments,elasticity of the membrane may have a bias or polarity that tends topermit elasticity in one or more directions, and tends to disallowelasticity in one or more other directions.

An aspect of the disclosed technology that is particularly advantageousin achieving a high resolution signal from which pressure profiles fromparticular physiologic sources (such as peritoneal pressure, respiratoryrate, and cardiac rate, relative pulmonary tidal volume, cardiac output,relative cardiac output, and absolute cardiac stroke volume) may bemonitored relates to adjusting and maintaining a balance of pressure oneither side of the pressure interface represented by the membrane of thepressure sensing balloon. This balance of pressure may be referred to asa pressure differential of zero, or as a zero pressure gauge. Pressureimpinging on the external face of balloon (facing the internal aspect ofthe bladder) is subject to change according to the physiology of thepatient. Pressure on the internal face of the balloon (which is in fluidcommunication with the fluid column) is subject to degradation becauseof fluid leakage and imperfect seals.

Upon first insertion of the Foley type catheter, external pressure istypically applied to the fluid column and against the pressure interfaceto a first approximation of pressure being exerted on the pressureinterface from within the bladder. Pressure signals, as measured acrossa pressure interface, have a maximal amplitude when the pressuredifferential is zero. Accordingly, the amplitude of a pressure signalcan be used to tune the pressure being applied from the fluid columnagainst the pressure interface. This process of applying an appropriateamount of pressure against the interface may be referred to as primingthe fluid column or priming the balloon. Inasmuch as pressures on eitherside of the pressure interface may change, as described above, the fluidcolumn may need to be reprimed or re-tuned, from time to time. Thenecessity of repriming can be monitored by testing small changes inpressure so as to achieve maximal amplitude of a pressure signalprofile.

Embodiments of the disclosed system and method include automaticpressure tuning by a controller. Accordingly, the tuning system candetect the optimum target pressure and volume to inflate the balloon bymonitoring sensed pressure signals and adding or removing air volume asneeded. For example, upon insertion of the catheter, a pressure tuningcircuit that regulates the balloon volume and pressure will inflate theballoon until it detects a physiologic-sourced pressure rate. Uponsensing that rate, the pressure tuning controller will add or subtractminute amounts of air in a routinized sequence until the amplitude ofthe sensed wave is greatest. The control feedback loop between theoptimally tuned pressure (manifesting as balloon pressure and volume)and the sensed physiologic pressure profile iterates continuously and oras needed to ensure high fidelity measurement of the physiologic data.In some embodiments, automatic pressure tuning may be performed in theapparent background while the physiologic data is being transmitted anddisplayed; in other embodiments the system may suspend transmission ofphysiologic data during a pressure tuning sequence.

Embodiments of the disclosed technology include a gas delivery systemthat can deliver gas in a priming operation, whereby pressure can beapplied to a fluid column proximal to the proximal-facing aspect of thepressure interface. A source of gas, such as compressed air or liquid isheld in a storage tank. Using CO₂ as an example, CO₂ is controllablyreleased from the storage tank through a pressure regulator that canstep pressure in the tank (for example, pressure of about 850 psi) downto the range of about 1 psi to about 2 psi. Released gas passes througha filter and a pressure relief valve set at about 2.5 psi. The pressurerelief valve is a safety feature that prevents flow through of gas at alevel greater than 2.5 psi in the event of failure of the upstreamregulator. CO₂ exiting the pressure relief valve next passes through afirst solenoid-controlled fill valve to enter the catheter line,ultimately filling the balloon that comprises the pressure-sensinginterface. Pressure within the balloon is allowed to rise to a level ashigh as 30 mm Hg, whereupon the first solenoid-controlled valve closes.A second solenoid-controlled valve, distal to the first valve operatesas a drain valve, which can release pressure from the catheter to atarget pressure. Alternatively, the drain valve may be activated until arespiratory waveform is detected after which the balloon will beoptimally primed and the valve will be closed. The drain valve may besubject to proportional control, operably based on voltage orpulse-width modulation (PWM), which allows a drain rate sufficientlyslow that the target pressure is reached and the valve can be closedprior to overshoot. Alternatively, a peristaltic or other air pump maybe utilized to fill the balloon with room air.

Intrabdominal pressure or bladder pressure, as sensed by an embodimentof the disclosed technology, may also be used to detect the level ofpatient movement (as may vary, for example, between substantially nomovement to a high level of movement) and to report the movement levelto a healthcare provider. A short burst of peaks and valleys in bladderpressure activity can serve as a proxy for body movement in that such abladder pressure profile is a strong indicator that the patient is usingtheir abdominal muscles, as, for example, to sit up or get out of bed.This embodiment may be of particular benefit for patients that are atrisk of falling. In a patient that is a fall-risk, a healthcare providermay be notified that the patient is sitting up and respond accordingly.Alternatively, the device may be used to report inactivity of a patientand/or lack of patient movement.

Embodiments of the technology may also report patient movement in thedetection or diagnosis of seizure disorder. In this embodiment, thepressure variations may trigger an EEG or recording equipment to allowfor intense period of monitoring during an episode suspected of being aseizure. In addition, or alternatively, a pressure sensor, acousticsensor or other sensors may be used to detect bowel activity, patientmovement, seizure activity, patient shivering, frequency of coughing,severity of coughing, sleep quality, speech detection, patientcompliance (movement or lack thereof), and may alert the healthcareprovider that the patient has not moved and must be turned or rolled.This movement-related information may also be relayed to a hypothermiadevice, a drug delivery device or other device to control or mitigateseizure activity, shivering and/or coughing.

Embodiments of the technology may also automatically adjust intravenousfluid or drug infusion rates based on feedback from the cardiac outputor respiratory rate sensed. In one such embodiment, a patient-controlledanalgesia pump may be deactivated if a respiratory rate drops too low.Respiratory depression can be fatal in this group and this safeguardwould prevent overdose. An automated feedback system may also beadvantageous in a large volume resuscitation procedure, wherein fluidinfusion can be tailored based on intraabdominal pressure to preventabdominal compartment syndrome by sounding an alert and slowing infusionrates as the intraabdominal pressure rises. Yet another automatedfeedback feature may provide direct feedback to a ventilator system toprovide the optimal pressure of ventilated gas. In the setting ofincreased abdominal pressure, typical ventilator settings do not providesufficient respiration for the patient. An automated adjustment of theventilator settings based on intraabdominal pressure feedback from thisembodiment may advantageously provide for optimal patient ventilation.Embodiments of the technology may also be applied as a correction in theapplication or understanding of other diagnostic measurements. Forexample, central venous pressure may be dramatically distorted in thesetting of elevated intraabdominal pressure. Providing direct access tothese data by the central venous pressure reporting system allows forthe automatic correction and accurate reporting of this criticalphysiologic parameter. Embodiments of the technology may also be used ina variety of other ways to automate therapy including infusion of fluidsthat may further include active agents, such as pressors or diuretics inresponse to increased or decreased cardiac output.

In some embodiments, the Foley type catheter is configured to report thepresence of a water droplet or other obstruction in an air-filled lumen,and then handle or resolve the droplet. In a hypothermic setting, inparticular, moisture in an air lumen can condense and form obstructivewater droplets. Water droplets in an air-filled lumen (or air bubbles ina water-filled lumen) can disturb or complicate pressure signals due tothe surface tension of the water. Accordingly, a pressure-transmissionlumen in some embodiments of the disclosed technology may include ahydrophilic feature (such as a coating on the wall of the lumen itself,or a hydrophilic fiber running the length of the lumen) to wick moistureaway from the lumen in order to maintain a continuous, uninterrupted airchannel. In some embodiments, a hygroscopic composition (silica gel, forexample) may be used in line with the air infusion line or within theair infusion lumen itself to capture water or humidity. In someembodiments, a hygroscopic composition may be included within thecatheter so that the air infusion circuit need not be serviced toreplace this material.

In some embodiments of the disclosed technology, air may also beintermittently (and automatically) infused and extracted into thepressure-sensing balloon so that the balloon is in a constant state ofbeing optimally primed, as described in further detail above. In thecase of the wicking fiber or hydrophilic coating in the lumen, the airextraction may also contribute to removing and trapping any water fromthe air line. In the instance of a liquid-filled lumen, a hydrophilicfiber or a hydrophilic coating on the inside of the pressure lumen willprovide similar benefit in allowing this lumen to handle an air bubble.In this instance, an air bubble may distort the signal, but the airwater interface surface tension is defused by a hydrophilic coating inthe lumen of the catheter.

Additionally, a custom extrusion and lumen shape may also be used toprevent obstruction in the case of liquid and/or air-filled lumens. Insome embodiments of the technology, for example, a Foley type cathetermay have a lumen that is stellate in cross sectional profile. Such alumen is generally immune from obstruction by a water droplet, as thedroplet tends to cohere to itself and push away from the hydrophobicwalls. This behavior tends to disallow filling of a cross-sectionalspace, and allows for an air channel to remain patent around the waterdroplet and communicate to the sensor. The same logic applies to an airbubble in water in a hydrophilic, stellate water lumen. In this instancethe hydrophilic liquid will cling to the walls and allow for acontinuous water column that excludes the air bubble to the center ofthe lumen. The same applies for a hydrophobic liquid in a hydrophobiclumen. In some embodiments, the catheter may include an air channel, anda sensor incorporated within the catheter itself or a fluid lumen thatis capable of transmitting the pressure back to a sensor.

In some embodiments, the sensing Foley catheter may include a bloodpressure sensing element that may take any of several forms. In oneembodiment, a blood pressure sensing element includes a pressuredelivery balloon 32 (either a separate, dedicated balloon or a balloonin fluid communication with a device retention balloon or a pressuresensing balloon) that can be optically analyzed as it is inflated todetermine at which pressure the vessels within the bladder or urethraare blanched and blood flow is stopped. This approach provides a readingof the perfusion pressure of the tissue abutting the pressure deliveryballoon, such reading reflective of both the systemic blood pressure andvascular resistance. This embodiment of a perfusion pressure device maybe used to provide early detection or monitoring of a variety of acuteor emergent medical conditions such as sepsis, shock, hemorrhage, andcan be particularly advantageous in detecting these conditions at anearly stage.

Other modalities may be used to detect that the tissue has been blanchedor ischemic, as well, with the common methodological aspect being thatof the intermittent inflation within the lumen, body cavity or bodilytissues to provide the compression of the vasculature. Embodiments ofthis device and associated methods may also be used to detect perfusionpressure in other areas of the body with an intermittently inflatablemember and optical detection of blood flow or the presence of blood.

Tissue perfusion information may also be provided by way of sensorsdisposed on the shaft of the catheter such that they contact theurethral wall when the catheter is in place. These sensing technologiesmay include microdialysis, pyruvate, lactate, pO₂, pCO₂, pH, perfusionindex, near-infrared spectroscopy, laser Doppler flowmetry, urethralcapnography, and orthogonal polarization spectroscopy. Any of thesetests may also be performed on the urine or the bladder wall itself togenerate measurements of tissue perfusion.

Embodiments of a sensing Foley catheter have been used to collect datafrom a human subject (FIGS. 7-9 ) and from a pig (FIGS. 10-11 ). Thehuman subject was a consenting and well-informed volunteer.

FIG. 7A shows an example of respiratory rate sensing data from a humansubject, as provided by an embodiment of the sensing Foley cathetersystem. During this test period, the subject performs a respiratorysequence as follows: (1) breath being held at the end of an expiration,(2) valsalva, (3) normal respiration, (4) valsalva, and (5) breath beingheld at the end of an expiration. FIG. 7B shows a detailed portion ofthe respiratory profile of FIG. 8A, a portion of the period of normalrespiration.

FIG. 8 shows an example of cardiac rate and relative cardiac outputsensing data from a human subject, as provided by an embodiment of thesensing Foley catheter system, and an EKG trace as measuredsimultaneously and independently.

FIG. 9 shows data related to relative cardiac output sensing in a humanleg raising exercise in which cardiac output increases, as demonstratedby an increased amplitude of the cardiac pulse.

The data shown in FIGS. 10 and 11 were derived from studies done withYorkshire pigs under IACUC-approved protocols. FIG. 10 shows an exampleof peritoneal sensing data, with a focus on respiratory rate from a pig,as provided by an embodiment of the sensing Foley catheter system. FIG.11 shows an example of pig study that demonstrates the capability of anembodiment of the sensing Foley catheter system to detectintra-abdominal hypertension. In this study, the peritoneal cavity wasaccessed with a 5 mm Tenamian trocar. The trocar was then attached to a5 L bag of Lactated Ringers solution via a peristaltic pump, and thesolution was infused at a rate of about 1 L per minute. Fluid flow wasdiscontinued once a pressure of about 20 mmHg was obtained after whichthere was no net fluid flow in or out of the cavity.

FIG. 13 provides a flow diagram of an embodiment of the method ofmonitoring pressure as it occurs dynamically as waves of variedfrequency and amplitude in the intraabdominal cavity, as detected fromwithin the urinary bladder. Through the agency of a pressure interface,a high fidelity pressure profile is generated and transmitted proximallythrough a fluid column. More proximally, a pressure transducer convertsthe high fidelity pressure wave into a high fidelity electrical signalthat is informative of pressure frequency and amplitude. The generatedhigh fidelity electrical signal is then processed to yield data subsetsthat are reflective of components within the overall pressure profile,such subsets being attributable to particular physiologic sources, suchas peritoneal pressure, respiratory rate, cardiac rate, relative cardiacoutput, and patient motion or activity.

Unless defined otherwise, all technical terms used herein have the samemeanings as commonly understood by one of ordinary skill in the medicalarts. Specific methods, devices, and materials are described in thisapplication, but any methods and materials similar or equivalent tothose described herein can be used in the practice of the presentinvention. While embodiments of the invention have been described insome detail and by way of illustrations, such illustrations are forpurposes of clarity of understanding only, and are not intended to belimiting. Various terms have been used in the description to convey anunderstanding of the invention; it will be understood that the meaningof these various terms extends to common linguistic or grammaticalvariations thereof. Further, while some theoretical considerations mayhave been advanced in furtherance of providing an understanding of thetechnology, the appended claims to the invention are not bound by suchtheory. Moreover, any one or more features of any embodiment of theinvention can be combined with any one or more other features of anyother embodiment of the invention, without departing from the scope ofthe invention. Still further, it should be understood that the inventionis not limited to the embodiments that have been set forth for purposesof exemplification, but is to be defined only by a fair reading ofclaims appended to the patent application, including the full range ofequivalency to which each element thereof is entitled.

What is claimed is:
 1. A measurement system, comprising: a catheterhaving a fluid lumen defined therethrough; a fluid column having apressure-transmitting column and a fluid within and which is disposed inthe catheter and coupled to a gas delivery system; a pressure interfacedisposed on the catheter, the pressure interface being in communicationwith the fluid column; a pressure transducer coupled to the fluid columnand configured to receive a pressure signal from the pressure interfacevia the fluid column; a controller configured to receive the pressuresignal from the pressure transducer and to control the gas deliverysystem to transmit pressure to the pressure interface via gas deliveryin response to receiving the pressure signal; a receptacle configured toreceive a flow of urine from a subject through the fluid lumen; and oneor more sensors in communication with the controller, wherein thecontroller is configured to detect an electrical property of the urinevia the one or more sensors and apply signal analysis and a predictivealgorithm on the detected electrical property and is further configuredto monitor a rate of the flow of urine and provide an alert when therate is outside of a predetermined range.
 2. The system of claim 1wherein the controller is further configured to monitor one or moreparameters of the urine relevant to kidney function.
 3. The system ofclaim 1 further comprising an infusion console in communication with thecontroller, wherein the infusion console is configured to controldelivery of an infusion fluid to the subject in response to inputreceived by the controller.
 4. The system of claim 1 wherein thecontroller is further configured to determine a level of an analyte fromthe urine.
 5. The system of claim 4 wherein the one or more sensors areconfigured to measure a content of the analyte comprising hemoglobin,protein, glucose, bacteria, blood, leukocyte esterase, or particulatematter.
 6. The system of claim 1 wherein the controller is furtherconfigured to receive external data from an external source andintegrate the external data with internal data within the controller. 7.The system of claim 1 wherein the gas delivery system comprises a pump.